Weining, Guizhou Tongchanghe Copper Geological Features And Metallogenic Prediction

Although the copper mineralization was known in vesiculate lava in the Emeishan Permian basalts and people had found dozens small ore bodies, these ore bodies are very small and discontinues, never economic copper deposit had been discovered. In 2002, ZhuBingquan discovered a large-scale copper deposit in Ludian area near the border area between Yunan and Guizhou provinces and brought forth a new theory about Emeishan basaltic copper deposits. Since that time, people started studying basaltic copper deposits again. This time, the object of our study is Tongchanghe basaltic copper deposit in Weining area of Guizhou province. Tongchanghe locates the east part of Emeishan Permian basalts. The basalts in Tongchanghe is dark-grey and dark-green, porphyritic texture and porphyaceous texture, fumarolic structure and amygdaoidal structure. It belongs to calc-alkali (a little alkali) tholeitic basalt according to its chemical composition. It is continental flood basalt with very high Cu background value. On Rittmann's diagram, the points are locate the 'interior plate structure' part. The rare elements composition suggests that it have the characteristic of continental rift eruption .The basalt have high Ti and low Mg value, it is the result of continental crust migmatization. The basalts can be divided to 3 eruptive cycles and P_2em^3-8 is the cardinal ledge. Ore bodies are bedded . stratoid and lenticalar in P_2em^3-8 .The basalt in P_2em^3-8 have been altered obviously ,the mineralization are tight associated with chloritization, silicatization, bituminization and pyritization . The distribution of ore bodies was controlled by faults, the ore bodies enriched where faults pass. The ore minerals are chalcopyrites, native coppers, chalcosites and green malachites. The ore are mainly euhedral-granual, hypidiomorphic-granual texture and filling-metasomatic texture, impregnation structure and joint vein structure.As to the deposit's genesis, there are many opinions. .ZhuBingquan thought it was mineralized by contemporaneous hydrothermal. Some people thought it was anaphase hydrothermal matallogenesis. The difference was on the hydrothermal' source. After investigation we think the Tongchanghe basaltic copper deposit is not resulted by single factor but rather the coupling amplification of the multi-factor .The Cu come from the late period of volcanic eruption ,the syngenetic hydrothermal made copper enriched primarily . After buried metamorphism,,the anaphase hydrothermal made progressive copper enrichment in ore.After investigation the cardinal ledge's distribution and the scale ,the wall-rock alteration, the mineralization signs , faults occurrence and the distribution of old mining pockets .We predicted Dachangpo and Sujiagou to have copper ores. In these two areas, the mineralization conditions are very good. We are confident that these tow areas have good potential ores.